The poison that got away

Anne Davies INVESTIGATIONS EDITOR

THE fishing bans in Sydney Harbour will have to stay in place for decades due to high levels of dioxins, despite an expensive clean-up of Homebush Bay, the original source of the contamination.

Although the clean-up of the former Union Carbide site is due to finish early next year, new figures obtained by the Herald under freedom of information laws show dioxins from the former pesticide factory have washed more than 10 kilometres up and downstream.

They cover an area too large to be remediated and authorities say the only answer is to wait until sediments cover the contaminated layer, so the poison cannot be absorbed by fish and small invertebrates.

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Even though the water quality in the harbour is much improved, the high levels of dioxins in areas where fish feed means the warning not to eat fish caught west of the Harbour Bridge, and to eat only 150 grams a month of fish caught east of the bridge, will likely remain for decades.

The data, collected by the NSW Department of Environment, Climate Change and Water in 2008, shows that large tracts of sediments in the harbour are more contaminated with dioxins than Tokyo Bay or New York Harbour, and are among the most contaminated in the world.

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The department sampled more than 25 sites. They showed that directly outside the remediation area in Homebush Bay dioxin levels were 610 picograms per gram of sediment compared with 2.3 for a relatively pristine estuarine environment.

But there were also readings of 350 picograms 10 kilometres up the Parramatta River and significant readings as far east as Rozelle.

Deadly catch ... Sara Gatavi reels in a fish at Woolwich. Carcinogenic chemicals from a former pesticides factory at Homebush are spreading throughout the harbour. Photo: Dallas Kilponen

The tests confirm that Union Carbide is the source. The contamination has a ''signature'' that matches the cocktail of dioxins produced by Union Carbide during manufacture of the now-banned pesticide 2,4,5-T and the defoliant, Agent Orange, used during the Vietnam War.

The department's director of specialised regulation, Craig Lamberton, said lifting the ban would be ''a medium- to long-term thing'' and that a large-scale clean-up would be technically and financially impractical.

Asked if the ban could last as long as 50 years, Mr Lamberton said: ''I don't want to predict, but that's the kind of thing we are talking about. We think it will be decades.

''This strategy is about treating the worst of the contaminants. We have stopped new contaminants going into the bay by digging up all the soil on the site and treating it [and] removing all of the highly contaminated spots in the bay.

''The dioxins that are unrecoverable will be covered up by clean material, which means they won't be accessible and won't be available in the environment. They will still be there, they will eventually break down, but it's literally decades.''

Dioxins are classified as carcinogens and, as well as cancers, have been linked to birth defects and skin conditions. The exact health effects at lower levels are unclear.

For more than 20 years, waste from the Union Carbide site was used for landfill and was dumped into the mangroves where it leached into Homebush Bay. Union Carbide was allowed to leave Australia without a comprehensive clean-up of the site and in the 1980s it was discovered that it was the main source of contamination in fish in the bay.

In the 1990s the NSW government bought the site and promised $20 million towards a clean-up but it took until 2004 to orchestrate the remediation. It was not until 2005 that alarm bells rang when bream and prawns with high dioxin levels were discovered.

However, the warning not to eat fish caught west of the bridge, imposed in late 2005, is being ignored by many recreational fishers. A survey by the Department of Industry published a month ago found that 25.3 tonnes of fish were caught and kept by fishers in 2007-08.

Many of the recreational fishers have English as a second language, raising serious questions about whether the warning is getting through.